What breaks the enchantment?

[littlemanpoet]

Warning:this thread may be hazardous to the enchantment Tolkien's stories weave on you. Proceed at your own risk.

Tolkien wanted his readers to experience "secondary belief", which is to experience the story of The Lord of the Rings (as well as his other writings) as "real", at least while we're reading, and maybe afterwards as well. This doesn't mean we're deluded into believing that it's really real, although some of us might wish it were; and perhaps some of us do choose to be so deluded (I did for a while).

Here's my question: What, in Tolkien's writings, breaks the spell for you? Why do you think this is so? Was it a failure on his part, or is it something you bring to the reading?

I'll give one example from my own experience. In re-reading the Prologue to FotR, recently, I came across the section where it says that Hobbits learned building from Men, specifically the Dúnedain, who learned it from the Elves. In all my previous readings, I had no problem with this. This time, however, the notion seemed ludicrous. Why would Hobbits and Men need Elves to teach them how to build? Are Hobbits and Men so stupid that they couldn't learn how to build on their own? It's comparable to saying that Native Americans could not have invented canoes, but needed Vikings to come to the new world to teach them how to build such boats.

So that broke the spell for me. I had to remind myself that Tolkien was using old sources in which the Fairy Folk are said to have taught neolithic humans to build. But for me it didn't work ... this time.

So, that's my example. Maybe it's just my problem.

But do you have a place in which the spell was broken for you?